Magnetic field producing apparatus

ABSTRACT

A magnetic field producing structure has a pair of U-shaped elongated core members with the end faces of the legs of one of the core members arranged in a confronting relationship across a predetermined gap with the end faces of the legs of the other one of the core members. A first winding on each of the core members is wrapped around the trough of each of the core members. A source of alternating current is arranged to serially energize the first windings on both of the core members. A second winding is located on each of the core members and is wrapped around the corresponding core member at right angles to the first winding. A direct current source is arranged to serially energize the second windings on the core members.

United States Patent [1 1 Ballinger MAGNETIC FIELD PRODUCING APPARATUS[75] inventor: Dale 0. Ballinger, Denver. C010. [73] Assignee:Honeywell, Inc.. Minneapolis. Minn. [22] Filed: Nov. 29. 1973 [21] Appl.No.: 420,284

[52] US. Cl. 360/56; 360/66; 360/123; 360/1 18 [51] Int. Cl....G1lb5/02; G1 1b 5/112; HOlf 13/00 [58] Field of Search 360/66. 118. 123. 56.115;

[ 56] References Cited UN1TED STATES PATENTS 2.498.423 2/1950 Howell360/118 2.550.753 5/1951 Andrews. 2.604.550 7/1952 Begun 2,908.76810/1959 Steinegger 2.928.078 3/1960 Hagopian 3.449.529 6/1969 Camras360/66 1 1 Apr. 22, 1975 Primary Examiner-Bernard Konick AssistantExaminer-Alan Faber Attorney. Agent. or Firm-Arthur H. Swanson; LockwoodD. Burton; Mitchell J. Halista ABSTRACT A magnetic field producingstructure has a pair of U- shaped elongated core members with the endfaces of the legs of one of the core members arranged in a confrontingrelationship across a predetermined gap with the end faces of the legsof the other one of the core members. A first winding on each of thecore members is wrapped around the trough of each of the core v members.A source of alternating current is arranged to serially energize thefirst windings on both of the core members. A second winding is locatedon each of the core members and is wrapped around the corresponding coremember at right angles to the first winding. A direct current source isarranged to serially energize the second windings on the core members.

4 Claims. 3 Drawing Figures MAGNETIC FIELD PRODUCING APPARATUSBACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present inventionrelates to magnetic field producing apparatus. More specifically, thepresent invention is directed to a magnetic field producing apparatusfor producing a rotating magnetic field vector having an orientation ina predetermined plane.

SUMMARY OF THE INVENTION An object of the present invention is toprovide an improved magnetic field producing means for producing arotating magnetic vector parallel to a predetermined plane.

In accomplishing this and other objects, there has been provided, inaccordance with the present invention, a magnetic field producing meansincluding a first magnetic field core member having a generally U-shaped cross-section, a first winding wrapped on the member encompassingthe trough of the U-shaped cross-section. A second winding is wrappedaround the outside of the core member to produce a magnetic fieldemanating from the U-shaped cross-section ends of the core member. Asecond U-shaped core member having a pair of coils mounted thereon in asimilar arrangement to the first core member is positioned on the otherside of a recording medium with the ends of the legs of the second coremember being aligned with the ends of the legs of the first core member.An alternating current source is arranged to energize the first coil oneach of the core members in a series circuit interconnection. The secondcoil on each of the core members is connected in a series circuit acrossa direct current source.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the presentinvention may be had when the following detailed description is read inconnection with the accompanying drawings, in which;

FIG. 1 is a pictorial illustration of a magnetic field producingstructure embodying the present invention,

FIG. 2 is a cross-sectional illustration of the structure shown in FIG.1 taken across the U-shaped crosssection of the core members used in themagnetic field producing structure, and

FIG. 3 is a cross-sectional illustration of the structure shown in FIG.1 taken along the length of the core members of the magnetic fieldproducing structure.

DESCRIPTION OF THE PREFERRED EMBODIMENT DETAILED DESCRIPTION cordingmedium with each capsule containing a suspension of a plurality ofmagnetically responsive, flakelike particles. The recording medium maybe prepared for recording thereon by erasing any prior recordingsthereon, i.e., pre-aligning all of the flake-like particles in anorientation having a major surface of each of the flake-like particlesparallel to the plane of the recording medium, i.e., parallel to therecording surface of the recording medium. In this position of theencapsulated particles, the recording medium presents a uniformappearance at its recording surface.

A recording may be subsequently made upon the recording medium byreorienting the flake-like particles in a limited area encompassing arecording element, i.e., the particles are reoriented into a positionperpendicular to the recording surface of the recording medium.Following such a recording operation, the recording medium may be againerased and the recording medium returned to its original state byreorienting the particles back into their original state, i.e., parallelto the recording surface of the recording medium. Thus, the samemagnetic field is used to prepare the recording medium from an originalstate having nonoriented particles and to erase a recording on arecording medium previously placed into a recorded state. In eithercase, the net result is to align the encapsulated particles into astatewherein the major face of each of the flakelike particles (the majorface of a particle is defined as a surface having a dimension severaltimes greater than any dimension defining the thickness of eachparticle) is aligned parallel to the recording surface of the recordingmedium to present a uniform appearance thereon. In order to produce sucha particle aligning operation, it is necessary to generate a magneticfield vector within the plane of the recording medium and within theencapsulated particles while continuously rotating the magnetic fieldvector within the plane of the magnetic particle to uniformly align themajor faces of the particles parallel with the recording surface of therecording medium. Such a uniform alignment operation is effective toproduce a uniform surface appearance on the recording medium since themajor faces of the particles are arranged to reflect incident radiationfrom the recording medium. The result of a particle alignment whereinonly one axis of the particles were aligned parallel with the recordingsurface of the recording medium would not assure the attainment of theuniformly reflective recording surface.

The core structure of the present invention is directed to a magneticfield generating structure for producing such a rotating magnetic fieldvector within a predetermined plane, i.e., the plane of the particleswithin the recording medium. The core structure includes a pair ofgenerally U-shaped elongated core elements 4 and 6. The core elements 4and 6 are arranged with the end faces of the legs of one of the U-shapedcore elements in a confronting relationship with the respective endfaces of the legs of the other one of the core elements. The end facesof the legs of the core element 4 are spaced from the end faces of thelegs of the core element 6 by a distance sufficient to allow therecording medium 2 to pass therebetween.

The following discussion is directed to a description of the structureof the energizing winding wound around one of the core members 4 and 6,i.e., a first core member 4, inasmuch as the arrangement of the windingson the second core member 6 is substantially identical. A firstenergizing winding 8 is arranged on the first core member 4 tolengthwise encircle the core member 4 in the trough of the U-shaped coremember. A first end of the first winding 8 is connected to one side of asource of an alternating current source 12 while the other end of thewinding 8 is arranged to be connected to one end of a similar secondwinding 9 on the second core member 6. The other end of the secondwinding 9 on the second core member 6 is connected to the other side ofthe alternating current source 12.

A third energizing winding 16 is wound around the first core member 4 atright angles to the first winding 8 and encompassing the U-shapedcross-section of the first core member 4. A first end of the secondwinding 16 is arranged to be connected to one side of a direct currentsource 18. The other end of the third winding 16 is arranged to beconnected to one end of a similar fourth winding on the second coremember 6. The other end of the fourth winding 20 on the second coremember 6 is connected to the other side of the direct current source 18.Accordingly, the alternating current source 12 is arranged to seriallyenergize the similar windings 8 and 9 on the first and second coremembers 4 and 6 while the direct current source 18 is arranged toserially energize the similar windings l6 and 20 on the first and secondcore members 4 and 6.

The energization of the third and fourth windings l6 and 20 by thedirect current source 18 is effective to produce corresponding constantmagnetic fields in the respective core members 4 and 6. The magneticfields produced by the energization of the windings l6 and 20 by thedirect current source 18 is shown in FIG. 3. As shown in this figure,the constant magnetic fields from the opposing core members emanate fromthe U- shaped cross-sectional ends of the core members 4 and 6. By aselection of either current flow or winding direction, these constantmagnetic fields are arranged in field opposing relationship within therecord medium accepting space between the confronting leg end faces ofthe core members 4 and 6. Further, the constant magnetic field in thisspace between the core members 4 and 6 is in a direction parallel to aplane in which a recording medium 2 is placed between the core members 4and 6. The recording medium 2 is shown in FIG. 3 as being positioned inthis plane by any suitable means (not shown) to allow the magnetic fieldto pass through the recording member 2 parallel to the recording surfaceand through the encapsulated magnetic particles of the recording member2.

Concurrently, the energization of the first and second windings 8 and 9by the alternating current source 12, is effective to produce a magneticfield emanating from the ends of the legs of the core members 4 and 6.The energization of the first and second windings 8 and 9 is arranged toproduce opposing magnetic fields at the confronting leg end faces of thecore members 4 and 6. in FIG. 2, there is shown a representation of amagnetic field occurring during one half-cycle of the energizationcurrent from the alternating current source 12. During the otherhalf-cycle of the energizing alternating current, the north and southpoles occurring at the ends of the legs of the core members 4 and 6would, of course, be interchanged. As may be seen from FIG. 2, theopposing relationship of the magnetic poles found at the confronting endfaces of the legs of the core members 4 and 6 produces a second magneticfield in the plane of the recording medium 2 located between the ends ofthe legs of the core members 4 and 6. While this second magnetic fieldis also parallel to the plane of the recording medium 2 and in themagnetic particles contained therein, the magnetic field from the secondmagnetic field is reoriented as a result of the interchange of the polesof the magnetic field on alternate cycles of the alternating currentenergizing signal. The two magnetic fields, i.e., the direct currentfield and the alternating current field, accordingly, combine in theplane of the recording medium to produce a net magnetic field. vectorwhich rotates in the plane of .the recording medium 2 and in themagnetic particles to orient the major surfaces of the flake-likeparticles parallel to the plane of the recording medium. Thisorientation of the flake-like particles with the surface of therecording medium 2 is effective to erase any prior recording from therecording medium 2 to prepare it for further recording. One example of amagnetic field producing structure constructed in accordance with thepresent invention and suitable for erasing the aforesaid magnetic flakerecording medium had 230 turns of No. 28 wire in each of the first andsecond windings 8 and 9 while the third and fourth windings each had1,220 turns of No. 28 wire. The first and second windings 8 and 9 wereenergized by an alternating current of 0.7 amperes while the third andfourth windings may be energized with a direct current of 0.5 amperes.The core members 4 and 6 were each made of soft iron arranged as aU-shaped channel having a total length of 6 inches and a leg height of 1inch. The confronting end faces of the core legs may be spaced apart adistance of 15 thousands of an inch to accommodate the recording medium2. Such a magnetic field producing structure produced a magnetic fieldwithin the recording medium 2 of approximately 200 Gauss.

Accordingly, it may be seen that there has been provided, in accordancewith the present invention, a magnetic field producing structure forproducing a rotating magnetic field vector within a predetermined plane.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A magnetic field producing apparatus comprisin a first U-shaped coremember;

a second U-shaped core member, said first core member having leg endfaces spaced a predetermined distance from confronting leg end faces ofsaid second core member;

a first winding wound on the trough of said first core member;

a second winding wound on the trough of said second core member;

a first energizing means arranged to serially energize said first andsecond windings;

a third winding wound around said first core member at right angles tosaid first winding;

a fourth winding wound around said second core member at right angles tosaid second winding, and

a second energizing means arranged to serially energize said third andfourth windings.

2. A magnetic field producing apparatus as set forth in claim 1 whereinsaid first energizing means is a source of alternating current. i

3. A magnetic field producing apparatus as set forth in claim 2 whereinsaid second energizing means is a source of direct current.

windings are energized by said first energizing means to producemutually opposing and variable amplitude magnetic fields across saidpredetermined distance.

1. A magnetic field producing apparatus comprising a first U-shaped coremember; a second U-shaped core member, said first core member having legend faces spaced a predetermined distance from confronting leg end facesof said second core member; a first winding wound on the trough of saidfirst core member; a second winding wound on the trough of said secondcore member; a first energizing means arranged to serially energize saidfirst and second windings; a third winding wound around said first coremember at right angles to said first winding; a fourth winding woundaround said second core member at right angles to said second winding,and a second energizing means arranged to serially energize said thirdand fourth windings.
 1. A magnetic field producing apparatus comprisinga first Ushaped core member; a second U-shaped core member, said firstcore member having leg end faces spaced a predetermined distance fromconfronting leg end faces of said second core member; a first windingwound on the trough of said first core member; a second winding wound onthe trough of said second core member; a first energizing means arrangedto serially energize said first and second windings; a third windingwound around said first core member at right angles to said firstwinding; a fourth winding wound around said second core member at rightangles to said second winding, and a second energizing means arranged toserially energize said third and fourth windings.
 2. A magnetic fieldproducing apparatus as set forth in claim 1 wherein said firstenergizing means is a source of alternating current.
 3. A magnetic fieldproducing apparatus as set forth in claim 2 wherein said secondenergizing means is a source of direct current.